/Engine/Source/Runtime/SlateCore/Public/Fonts/FontCache.h
Calculates the kerning amount for a pair of characters
The kerning amount, 0 if no kerning
int8 GetKerning ( const [FFontData](API\Runtime\SlateCore\Fonts\FFontData) & InFontData, const float InSize, TCHAR First, TCHAR Second, float Scale ) const